In a steam pipeline of a steam turbine or the like which is provided in a power generation facility or the like, a steam valve for adjusting the flow rate of steam which is supplied or stopping the supply of the steam is provided.
The steam valve is provided with a casing with a flow path for steam formed therein, and a valve body movably provided in the flow path. A valve seat capable of being blocked by the valve body is formed in the flow path of the casing. The valve body is driven, thereby coming close to and being separated from the valve seat. In this way, a steam flow rate is adjusted by changing the flow path area of the gap between the valve body and the valve seat.
Incidentally, in such a steam valve, vibration or noise is generated due to a drift, a swirling current, or the like of high-pressure steam. For this reason, in order to reduce vibration or noise which is generated, improvement of the shape of the valve body or the valve seat of the steam valve is performed.
For example, PTL 1 discloses a steam valve in which the radius of curvature of a valve body is set to be in a range of 0.52 to 0.6 times the diameter (a seat diameter) of a portion where the valve body and a valve seat come into contact with each other and the radius of curvature of the valve seat is set to be greater than 0.6 times the seat diameter. According to this steam valve, a state where a streamline of steam is along a movement direction of the valve body is created, and thus a steam stream becomes stable, whereby it is possible to reduce vibration or noise of each portion of the steam valve.
Further, PTL 2 discloses a steam valve having a tapered surface inclined further toward the relative movement direction side of a valve body with respect to a valve seat than a valve head portion, on the upstream side of the valve head portion. According to this steam valve, the tapered surface inclined further toward the valve body movement direction side than the valve head portion is provided on the upstream side of the valve head portion, and therefore, before steam passes through the flow path between the valve seat and the valve body, the steam is guided by the tapered surface so as to head toward the valve seat movement direction. For this reason, it is possible to reduce vibration of each portion of the steam valve.